The imaginal discs of Drosophila offer an excellent system for the study of many developmental processes. Not only are the discs physically distinct from each other as well as from the rest of the organism, but certain of the developmental decisions which they undergo are temporally separated and are therefore amenable to study. The overall objectve of this research is to use the imaginal disc as a model system with which to genetically analyze the mechanism(s) of pattern formation. We are especially interested in learning more about the role of developmental compartmentalization - that process by which the imaginal disc is subdivided into groups of cells with different developmental fates. During the past nine months of this grant, I have been approaching this general topic by 1) analyzing the mechanism(s) of action of homeotic mutation, 2) investigating the role of cell death in regenerating imaginal discs and 3) developing techniques which will enable us to biochemically analyze the similarities and the differences between individual imaginal discs. The results of these experiments have indicated that homeotic structures do not arise as a result of "copying mistakes" made during regenerative growth but are mot likely due to the inactivation of certain essential regulatory proteins. We are presently developing and perfecting the analytical techniques necessary to provide molecular data and interpretations to these developmental questions. BIBLIOGRAPHIC REFERENCE: Arking, R. and Vlach, B. (1976) Direct selection of mutants of Drosophila resistent to juvenile hormone analogues. J. Insect. Physiol. 22: 1143-1151.